JP2019207767A - Manufacturing method of power storage device - Google Patents

Abstract

To provide a manufacturing method of power storage device capable of shortening the time required for weldment process, while restraining occurrence of poor weld.SOLUTION: A protective member 40 is used for manufacturing a secondary cell. Assuming the direction of laminating tabs 26 constituting a tab group 15 as the lamination direction of the tabs 26, the protective member 40 has multiple holes 41 penetrating in the lamination direction of the tabs 26. A manufacturing method of secondary cell includes an arrangement step of arranging the tab group 15 between a conductive member 17, i.e., a part of terminal structure, and the protective member 40, and a weldment step of forming a weld zone 45 while pressing the protective member 40 toward the tab group 15. In the weldment step, the tab group 15 is irradiated with laser by a laser irradiation device 70 from the protective member 40 side, and the laser irradiation device 70 is moved across multiple holes 41.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a power storage device having a welded portion between a tab group and a conductive member.

  Conventionally, vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles) have been mounted with lithium-ion secondary batteries or nickel-hydrogen secondary batteries as power storage devices that store power supplied to electric motors and the like. . The secondary battery disclosed in Patent Literature 1 connects an electrode assembly having a tab group in which a plurality of electrodes are stacked and tabs protruding from one edge of the electrode are stacked, and the electrode assembly and an external device. And a flat plate-shaped protective member disposed on the tab group. The protective member is thicker than the tab. The material of the protection member is, for example, the same kind of metal as the tab. The tab group is located between the conductive member and the protective member which are part of the terminal structure. Of the plurality of tabs constituting the tab group, the tab positioned at one end in the stacking direction faces the conductive member, and the tab positioned at the other end in the stacking direction faces the protective member. The secondary battery includes a welded portion in which a tab group, a conductive member, and a protective member are welded.

  Such a method for manufacturing a secondary battery includes a welding step of welding the tab group, the conductive member, and the protective member. A welding process is performed by irradiating a laser toward a tab group from the other end side of a lamination direction with a laser irradiation apparatus, for example. In the welding process, as a preparation for laser irradiation, the protective member is pressed against the tab group by a jig so that the tabs constituting the tab group are brought into close contact with each other. The laser is irradiated in a state where the jig presses the tab group via the protective member. Without a protective member, the tab located at the other end in the stacking direction floats from the other tabs due to heat shrinkage, and there is a gap between the raised tab and the other tab, resulting in poor welding between the tabs. There is. The protective member regulates the lifting of the tab located at the other end in the stacking direction. Thereby, since a welding process is performed in the state which the tabs which comprise a tab group closely_contact | adhere, generation | occurrence | production of the welding defect of tabs is suppressed.

JP-A-2006-219274

  However, in the welding process using the protection member, the time required for the welding process becomes longer as the protection member is melted compared to the welding process not using the protection member. If the time required for the welding process becomes long, the production efficiency of the secondary battery is lowered, which is not preferable. If the thickness of the protective member is reduced, the time required for the welding process can be shortened. However, if the thickness of the protective member is made too thin, the force with which the protective member presses the tab group toward the conductive member is insufficient. Then, the tab group and the conductive member are not welded, and poor welding between the tab group and the conductive member may occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a power storage device that can suppress the occurrence of poor welding and reduce the time required for the welding process.

  A method of manufacturing a power storage device for solving the above problems includes an electrode assembly having a tab group in which a plurality of electrodes are stacked and tabs protruding from one edge of the electrode are stacked, and the electrode assembly And a welding part laser-welded in a state where the tab group and the terminal structure are overlapped with each other, and the tab group is configured When the direction in which the tabs are stacked is defined as the tab stacking direction, a protection member having a plurality of holes penetrating in the tab stacking direction is used, and the tab group is disposed between the terminal structure and the protection member. An arrangement step of arranging, and a welding step of forming the welded portion while pressing the protective member toward the tab group. In the welding step, the tab group from the protective member side by a laser irradiation device. Leh towards Irradiates a and summarized in that moving the laser irradiation device so as to straddle the plurality of holes.

  According to this, in the part where the hole is formed in the protection member, the laser irradiated from the laser irradiation device passes through the hole and reaches the tab group. Since the tab group starts to melt from the portion exposed from the hole of the protective member, the welded portion can be formed without melting the protective member. Therefore, compared with the case where a welding process is performed using a protective member without a hole, the time required for the welding process can be shortened.

  Further, when welding is performed without using a protective member, conventionally, laser irradiation is performed while pressing a portion of the tab group outside the portion where the welded portion is formed with a jig or the like. At this time, in the tab group, the portion pressed by the jig is preferably in the vicinity of the portion irradiated with the laser. However, since the welded portion is formed in a line shape or a surface shape, depending on the part, the portion pressed by the jig is changed to the portion irradiated with the laser due to factors such as interference between the jig and the laser irradiation device. There are times when it cannot be approached. In this case, it has been difficult to press the tab group so that the lifting of the tab is restricted over the entire portion where the weld is formed. When the protective member is used, since the portion where the hole is not formed is adjacent to the hole, the entire portion where the hole is not formed can press the vicinity of the portion irradiated with the laser in the tab group. . Therefore, by using the protective member, it is possible to regulate the lifting of the tab over the entire portion of the tab group where the welded portion is formed. As a result, poor welding between the tabs can be suppressed. Moreover, since it is not necessary to melt the part in which the hole is not formed in the protection member, the thickness of the protection member can be increased in order to give the protection member sufficient strength for pressing the tab group. Therefore, the tab group can be sufficiently pressed toward the conductive member by the protective member. As a result, poor welding between the tab group and the conductive member can be suppressed.

  Further, with respect to the method for manufacturing the power storage device, the terminal structure includes a plate-like conductive member on which the weld is formed, and a lead terminal connected to the conductive member and connecting the inside and outside of the power storage device, The protective member preferably has a three-dimensional structure.

  According to this, the rigidity of the protection member with respect to the stacking direction of the tabs is higher than when the protection member does not have a three-dimensional structure. Therefore, deformation of the protective member when the protective member is pressed toward the tab group can be suppressed.

Moreover, it is preferable that the manufacturing method of the said electrical storage apparatus includes the removal process which removes the said protection member after the said welding process.
According to this, the protective member can be used repeatedly.

  Moreover, about the manufacturing method of the said electrical storage apparatus, in the said welding process, the said protection member is welded with the said tab group and the said terminal structure, the said protection member welded to the said tab group, and the said electrode which has the said tab group An attaching step of inserting an insulating member between the tab side end surface of the assembly, and when the insulating member comes into contact with the protective member in the attaching step, the protective member is elastic in the stacking direction of the tabs; It is preferable to deform.

According to this, in an attachment process, although an insulating member may contact a protection member, a protection member elastically deforms in the lamination direction of a tab. Therefore, the insertion of the insulating member is not hindered.
In the method for manufacturing the power storage device, it is preferable that expanded metal is used for the protective member.

  According to this, the cost of a protection member can be reduced compared with the case where the plate-shaped member which formed the several through-hole in the fin with which a peak and a trough are repeated is made into a protection member, for example.

  According to the present invention, it is possible to suppress the occurrence of poor welding and shorten the time required for the welding process.

The disassembled perspective view of the secondary battery of embodiment. Sectional drawing of a secondary battery. (A) is a perspective view which shows an arrangement | positioning process, (b) is the elements on larger scale of (a). Sectional drawing which shows the molten state of the tab group and conductive member in a welding process. The figure which observed the cross-sectional metal structure of the welding part under the microscope. Sectional drawing which shows another example of a secondary battery.

Hereinafter, an embodiment in which a method for manufacturing a power storage device is embodied in a method for manufacturing a secondary battery will be described with reference to FIGS.
As shown in FIG. 1, a secondary battery 10 as a power storage device includes a case 11 and an electrode assembly 12 accommodated in the case 11. The case 11 includes a rectangular parallelepiped case main body 13 and a rectangular flat lid 14 that closes the opening 13 a of the case main body 13. In the lid 14, a surface facing the inner side of the case 11 is an inner surface 14 a, and a surface facing the outer side of the case 11 is an outer surface 14 b. Both the case main body 13 and the lid 14 constituting the case 11 are made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a prismatic battery whose appearance is square. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

  As shown in FIG. 2, the electrode assembly 12 includes a plurality of positive electrodes 21, negative electrodes 22, and separators 23. The electrode assembly 12 has a layered structure in which separators 23 are interposed between the positive electrode 21 and the negative electrode 22 and are laminated in a mutually insulated state. The direction in which the positive electrode 21 and the negative electrode 22 are stacked is defined as a stacking direction.

  The positive electrode 21 has a rectangular sheet-like positive electrode metal foil 24 and a positive electrode active material layer 25 present on both surfaces of the positive electrode metal foil 24. The material of the positive electrode metal foil 24 of the present embodiment is aluminum (melting point: about 660 degrees). The positive electrode 21 includes a tab side edge portion 21a at one edge portion of the edge portions along the pair of long sides. The positive electrode 21 has a rectangular positive electrode tab 26 protruding from a part of the tab side edge 21a. The positive electrode tab 26 is formed of the positive electrode metal foil 24 itself without the positive electrode active material layer 25. The negative electrode 22 includes a rectangular sheet-like negative electrode metal foil 27 and negative electrode active material layers 28 present on both sides of the negative electrode metal foil 27. The material of the negative electrode metal foil 27 of the present embodiment is copper (melting point: about 1085 degrees). The negative electrode 22 includes a tab side edge portion 22a on one edge portion of the edge portions along the pair of long sides. The negative electrode 22 has a rectangular negative electrode tab 26 protruding from a part of the tab side edge 22a. The negative electrode tab 26 is composed of the negative electrode metal foil 27 itself without the negative electrode active material layer 28. The separator 23 is made of a rectangular sheet-like insulating material. The separator 23 insulates the positive electrode 21 and the negative electrode 22 from each other.

  The electrode assembly 12 includes a positive electrode tab group 15 in which the positive electrode tabs 26 of the positive electrode electrodes 21 are gathered and stacked on one end side in the stacking direction, and the negative electrode tab 26 of each negative electrode electrode 22 on one end side in the stacking direction. And a negative electrode tab group 15 stacked together. The positive electrode tab group 15 and the negative electrode tab group 15 are arranged side by side at intervals in the direction along the tab side edge portions 21a and 22a. The electrode assembly 12 has a tab-side end surface 12a on an end surface where the positive electrode tab group 15 and the negative electrode tab group 15 are present.

  As shown in FIG. 1, a positive electrode tab group 15 is joined with a rectangular plate-like conductive member 17 that is a part of a positive electrode terminal structure 16 described later and an electrode assembly 12. Further, the negative electrode tab group 15 is joined with a rectangular plate-like conductive member 17 which is a part of the electrode assembly 12 and a later-described negative electrode terminal structure 16. Each conductive member 17 is disposed between the inner surface 14 a of the lid 14 and the tab side end surface 12 a of the electrode assembly 12 along the inner surface 14 a of the lid 14.

  The length of each conductive member 17 is a crank shape extending in the longitudinal direction of the lid 14, and the short side of each conductive member 17 extends in the stacking direction. At the end in the longitudinal direction of each conductive member 17, the end near the center in the longitudinal direction of the lid 14 is one end, and the end located on the short edge side of the lid 14 is the other end. The positive electrode conductive member 17 includes an electrode bonding portion 17a bonded to the positive electrode tab group 15 at one end portion in the longitudinal direction, and an extraction terminal 31 that is a part of the positive electrode terminal structure 16 at the other end portion in the longitudinal direction. The terminal joining part 17b joined is provided. Similarly, the negative electrode conductive member 17 includes an electrode bonding portion 17a bonded to the negative electrode tab group 15 at one end portion in the longitudinal direction, and a lead that is a part of the negative electrode terminal structure 16 at the other end portion in the longitudinal direction. A terminal joint 17b joined to the terminal 31 is provided. There is a gap between the electrode joint portion 17 a of each conductive member 17 and the inner surface 14 a of the lid 14.

  The positive terminal structure 16 is disposed on one end side in the longitudinal direction of the lid 14, and the negative terminal structure 16 is disposed on the other end side in the longitudinal direction of the lid 14. Each of the positive and negative terminal structures 16 includes a lead terminal 31 connected to the conductive member 17. Each extraction terminal 31 has a plate-like base portion 31a and a shaft portion 31b protruding from the base portion 31a. The lead terminal 31 exchanges electricity with the electrode assembly 12. The base 31 a of the positive lead terminal 31 is electrically connected to the terminal joint 17 b of the positive conductive member 17, and the base 31 a of the negative lead terminal 31 is electrically connected to the terminal joint 17 b of the negative conductive member 17. It is connected to the. The distal end portion of the shaft portion 31b of each extraction terminal 31 penetrates the lid 14 and protrudes to the outside of the case 11, and is crimped. The shaft portion 31 b of the lead terminal 31 connects the inside and outside of the secondary battery 10. Each of the positive electrode and negative electrode terminal structures 16 includes a terminal joining member 32 that is electrically connected to the shaft portion 31 b of the lead terminal 31 outside the case 11, and an external connection terminal 33 that is electrically connected to the terminal joining member 32. With. A bus bar as an external device (not shown) that electrically connects the secondary batteries 10 to each other can be fixed to the external connection terminal 33. Each terminal structure 16 electrically connects the electrode assembly 12 and the bus bar.

  As shown in FIGS. 1 and 2, the secondary battery 10 includes an outer insulating member 34 that insulates the terminal bonding member 32 from the lid 14 on the outer surface 14 b of the lid 14. The secondary battery 10 includes an inner insulating member 35 in the case 11 that insulates the base portion 31 a of the lead terminal 31 from the lid 14. The electrode assembly 12, the lid 14, the positive and negative terminal structures 16, the outer insulating member 34, and the inner insulating member 35 are integrated as a lid terminal assembly W.

  The secondary battery 10 includes an insulating sheet 36 that covers the electrode assembly 12. The insulating sheet 36 covers five surfaces of the electrode assembly 12 excluding the tab side end surface 12a. The insulating sheet 36 insulates the five surfaces excluding the tab side end surface 12 a of the electrode assembly 12 from the inner surface of the case body 13.

  As shown in FIG. 2, the secondary battery 10 includes a positive electrode welded portion in which the positive electrode tab group 15 and the positive electrode conductive member 17 are laser welded, and a negative electrode tab group 15 and the negative electrode conductive member 17 in the laser beam. And a welded portion 45 of the welded negative electrode. Each welding part 45 of this embodiment is planar. The longitudinal direction of each welded portion 45 is along the longitudinal direction of the conductive member 17, and the short direction of each welded portion 45 is along the shortwise direction of the conductive member 17.

  The secondary battery 10 includes an insulating cover 50 disposed between the tab-side end surface 12 a of the electrode assembly 12 and the inner surface 14 a of the lid 14. The insulating cover 50 is attached to the lid terminal assembly W from the other end side in the stacking direction.

  The insulating cover 50 includes a case-side insulating portion 51 having a rectangular plate shape. The case-side insulating portion 51 covers the positive and negative electrode tab groups 15 from the other end side in the stacking direction, and insulates the front ends of the positive and negative electrode tab groups 15 from the inner surface of the case body 13. Therefore, the case-side insulating portion 51 is interposed between the positive and negative electrode tab groups 15 and the case body 13 on the other end side in the stacking direction.

  The insulating cover 50 is a rectangular plate-shaped lid extending from one long side near the lid 14 toward one end in the stacking direction, out of a pair of long edges of the case-side insulating portion 51 extending in the longitudinal direction of the lid 14. A side insulating portion 52 is provided. The length of the lid-side insulating portion 52 extends in the longitudinal direction of the lid 14, and the short side of the lid-side insulating portion 52 extends in the stacking direction. The lid-side insulating portion 52 is interposed between the electrode joint portion 17a of the positive electrode conductive member 17 and the inner surface 14a of the lid 14, and between the electrode joint portion 17a of the negative electrode conductive member 17 and the inner surface 14a of the lid 14. Insulating the positive and negative electrode conductive members 17 and the lid 14. The lid-side insulating portion 52 is supported by the electrode joint portion 17a of the positive and negative conductive members 17. The lid-side insulating portion 52 includes short edge portions 52a along the stacking direction at both ends in the longitudinal direction. One short edge portion 52a is located closer to the negative electrode terminal structure 16, and the other short edge portion 52a is located closer to the positive electrode terminal structure 16.

  As shown in FIG. 1, the insulating cover 50 extends from one end portion of the long edge portion near the electrode assembly 12 to one end side in the stacking direction of the pair of long edge portions of the case-side insulating portion 51. A plate-like negative electrode side insulating portion 53 is provided. The negative electrode side insulating portion 53 includes a rectangular tab side insulating portion 53 a as an insulating member that overlaps a part of the lid side insulating portion 52, as viewed from the thickness direction of the lid side insulating portion 52, and the lid side insulating portion 52. It has a rectangular terminal-side insulating part 53b that protrudes from one short edge part 52a. The dimension of the tab side insulating part 53a along the stacking direction is shorter than the dimension of the terminal side insulating part 53b along the stacking direction.

  As shown in FIG. 2, the negative electrode tab group 15 is located in a space surrounded by the negative electrode conductive member 17, the case side insulating part 51, and the tab side insulating part 53 a of the negative electrode side insulating part 53. The tab side insulating portion 53a of the negative electrode side insulating portion 53 is interposed between the negative electrode tab group 15 and the tab side end surface 12a of the electrode assembly 12, and covers the negative electrode tab group 15 from the electrode assembly 12 side. The tab-side insulating portion 53 a insulates the negative electrode tab group 15 from the electrode assembly 12. The terminal-side insulating portion 53b is interposed between the terminal joint portion 17b of the negative electrode conductive member 17 and the tab side end surface 12a of the electrode assembly 12, and the terminal joint portion 17b of the negative electrode conductive member 17 is disposed on the electrode assembly 12 side. Cover from. The terminal-side insulating portion 53 b insulates the negative electrode conductive member 17 from the electrode assembly 12.

  As shown in FIG. 1, the insulating cover 50 extends from the other end portion of the long edge portion near the electrode assembly 12 to the one end side in the stacking direction among the pair of long edge portions of the case-side insulating portion 51. The plate-shaped positive electrode side insulating part 54 is provided. The positive electrode side insulating part 54 includes a rectangular tab side insulating part 54 a as an insulating member that overlaps a part of the lid side insulating part 52, as viewed from the thickness direction of the lid side insulating part 52, and the lid side insulating part 52. A rectangular terminal-side insulating portion 54b protruding from the other short edge portion 52a. The dimension of the tab side insulating part 54a along the stacking direction is shorter than the dimension of the terminal side insulating part 54b along the stacking direction.

  Although not shown, the positive electrode tab group 15 is located in a space surrounded by the positive electrode conductive member 17, the case side insulating part 51, and the tab side insulating part 54 a of the positive electrode side insulating part 54. The tab-side insulating portion 54a of the positive-side insulating portion 54 is interposed between the positive-electrode tab group 15 and the tab-side end surface 12a of the electrode assembly 12, and covers the positive-electrode tab group 15 from the electrode assembly 12 side. The tab-side insulating portion 54 a insulates the positive electrode tab group 15 from the electrode assembly 12. The terminal-side insulating portion 54b is interposed between the terminal joint portion 17b of the positive electrode conductive member 17 and the tab side end surface 12a of the electrode assembly 12, and the terminal joint portion 17b of the positive electrode conductive member 17 is disposed on the electrode assembly 12 side. Cover from. The terminal-side insulating portion 54 b insulates the positive electrode conductive member 17 from the electrode assembly 12.

  Next, a method for manufacturing the secondary battery 10 will be described. The manufacturing method of the secondary battery 10 includes an assembling process for manufacturing the lid terminal assembly W, an attaching process for attaching the insulating cover 50 to the lid terminal assembly W, and a lid terminal assembly W to which the insulating cover 50 is attached. A housing step of housing in the case 11.

  In the assembly process, first, a joining process for integrating the terminal structure 16, the outer insulating member 34, and the inner insulating member 35 with the lid 14 is performed. In the joining step, the base portion 31 a of the lead terminal 31 that is a part of the terminal structure 16 and the terminal joint portion 17 b of the conductive member 17 are joined. Next, after the inner insulating member 35 is disposed on the conductive member 17, the lid 14 is disposed on the inner insulating member 35. Next, the outer insulating member 34 is disposed on the lid 14, and the terminal bonding member 32 is disposed on the outer insulating member 34. The shaft portion 31 b of the lead terminal 31 passes through the inner insulating member 35, the lid 14, the outer insulating member 34, and the terminal bonding member 32. Next, the tip end portion of the shaft portion 31 b of each extraction terminal 31 is caulked and fixed to the lid 14.

  Next, a foil collecting step of collecting the plurality of tabs 26 included in the electrode assembly 12 to form the tab group 15 is performed. In the foil collecting step, all the tabs 26 of the electrode assembly 12 are arranged on the conductive member 17 placed on a work table (not shown). Next, a tab group 15 is formed by pressing all the tabs 26 from the opposite side of the conductive member 17 with the tabs 26 sandwiched by a foil collecting device (not shown). The conductive member 17 faces the tab 26 positioned at one end in the stacking direction among the plurality of tabs 26 constituting the tab group 15.

  Next, as shown in FIG. 3A, an arrangement step of arranging a thin plate-like protective member 40 on the tab group 15 is performed. In the above-described joining step, the terminal structure 16, the outer insulating member 34, and the inner insulating member 35 are integrated with the lid 14, but in FIG. 3A, other than the lid 14 and the conductive member 17. Illustration of a member integrated with the lid 14 is omitted.

  As shown in FIG. 3B, the protective member 40 is a rectangular plate-like thin plate having a plurality of holes 41 penetrating in the thickness direction. In the present embodiment, the material of the protective member 40 disposed on the positive electrode tab group 15 is copper (melting point: about 1085 degrees), and the material of the protective member 40 disposed on the negative electrode tab group 15 is tungsten ( Melting point: about 3387 degrees). Further, the protection member 40 of the present embodiment has a three-dimensional structure, and specifically is an expanded metal. Expanded metal is manufactured by forming a plurality of slits in a staggered pattern on a flat metal plate and expanding the metal plate using the slits. The protection member 40 has a shape in which a plurality of wavy portions 42 extending in the short direction and repeating peaks and valleys in the thickness direction are arranged in the longitudinal direction. In addition, the three-dimensional structure described here refers to a structure in which the thickness of the base material is increased by deforming and processing the base material. The protection member 40 can be elastically deformed in the thickness direction by the wavy portion 42. In the wave portions 42 adjacent to each other in the longitudinal direction, a peak of one wave portion 42 and a valley of the other wave portion 42 are connected, and a valley of one wave portion 42 and a peak of the other wave portion 42 Are separated. A gap between the wavy portions 42 is a hole 41 of the protection member 40. In this embodiment, the opening ratio of the protection member 40 is about 50%.

  In the arranging step, the protective member 40 is arranged on the tab group 15 so that the short direction coincides with the protruding direction of the tab group 15 from the tab side end face 12a and the thickness direction coincides with the stacking direction of the tabs 26. The That is, the direction through which the hole 41 of the protection member 40 penetrates and the direction in which the protection member 40 can be elastically deformed coincide with the stacking direction of the tabs 26. Accordingly, the tab group 15 is located between the conductive member 17 and the protection member 40. Of the plurality of tabs 26 constituting the tab group 15, the tab 26 positioned at the other end in the stacking direction is opposed to the protection member 40 and is shielded by the waved portion 42 of the protection member 40, and the protection member 40. Part exposed from the hole 41. Further, a part of the tab 26 located at the other end in the stacking direction intermittently contacts the protective member 40 by the valleys of the wave-like portions 42 of the protective member 40.

  Next, a welding process is performed in which the tab group 15 and the conductive member 17 are laser-welded while pressing the protective member 40 toward the tab group 15. The end portion of the protection member 40 is pressed toward the tab group 15 by a pressing device (not shown) disposed above the protection member 40. Then, a reaction force acts on the protection member 40 from the tab group 15. However, since the protection member 40 has a three-dimensional structure, the protection member 40 has sufficient rigidity in the stacking direction of the tabs 26. Furthermore, the protection member 40 of this embodiment is an expanded metal, and the troughs of the wavy portions 42 of the protection member 40 that intermittently contact the tab group 15 can be elastically deformed. Therefore, in the portion where the welded portion 45 is formed in the tab group 15, the valley of the wave-shaped portion 42 of the entire protection member 40 can contact the tab group 15 and press the tab group 15 toward the conductive member 17. Thereby, the tabs 26 adjacent to each other in the stacking direction constituting the tab group 15 and the tab group 15 and the conductive member 17 are in close contact with each other.

  The tab group 15 and the conductive member 17 are welded in a state where the tabs 26 and the tab group 15 and the conductive member 17 are in close contact with each other. Welding is performed by a laser irradiation device 70 disposed above the protective member 40. The laser irradiation device 70 moves from one end in the longitudinal direction of the protection member 40 toward the other end while reciprocating in the short direction of the protection member 40. The laser irradiation device 70 irradiates the protective member 40 with a continuous wave laser while moving.

  When the laser irradiation device 70 irradiates the laser while moving over the protection member 40, the laser is continuously irradiated across the hole 41 of the protection member 40. For this reason, since the tab group 15 is shielded by the protection member 40 at a portion where the hole 41 does not exist in the protection member 40, the laser hardly reaches the tab group 15. On the other hand, in the portion where the hole 41 exists in the protection member 40, the laser reaches the tab group 15 after passing through the hole 41 of the protection member 40. Therefore, in the tab group 15, the portions irradiated with the laser and the portions not irradiated with the laser appear alternately. The spot diameter of the laser irradiated on the tab group 15 passes through the hole 41 of the protective member 40 and is smaller than the diameter immediately after irradiation.

  As shown in FIG. 4, in the tab group 15 where the laser is irradiated and in the vicinity thereof, the melting of the tab group 15 proceeds rapidly, and the molten metal is pushed and spread by the recoil force of the metal vapor. A hole H is formed. The laser penetrates into the formed keyhole H and undergoes multiple reflections within the keyhole H. Thereby, the depth of the keyhole H becomes deeper. When the deepest portion of the keyhole H reaches the conductive member 17, the tab group 15 and the conductive member 17 are welded to form a welded portion 45. Thereafter, when the weld 45 is solidified, the keyhole H is filled with the surface tension of the molten metal. Note that spatter S is generated during welding, but part of the generated spatter S adheres to the protective member 40.

  As shown in FIGS. 4 and 5, the penetration depth of the welded portion 45 in the portion where the keyhole H is formed is deeper than the penetration depth of the welded portion 45 around the keyhole H. As described above, in order to irradiate the laser by moving the laser irradiation device 70 so as to straddle the plurality of holes 41 of the protection member 40, the weld 45 is cut in the depth direction along the longitudinal direction of the protection member 40. In the cross section, portions where the weld portion 45 has a deep penetration depth and portions where the weld portion 45 has a shallow penetration depth appear alternately. As a result, as shown in FIG. 5, the welded portion 45 exhibits a metal structure in which the solidified portion after melting overlaps the moving direction of the laser irradiation device 70, that is, the longitudinal direction of the protective member 40.

  As described above, the melting point of the material of the protection member 40 is higher than the melting point of the material of the tab group 15. For this reason, in the welding process, even if the laser irradiation conditions are set so that the deepest part of the keyhole H reaches the conductive member 17, the protective member 40 hardly melts. In other words, the laser irradiation conditions are set such that the temperature of the portion irradiated with the laser exceeds the melting point of the tab 26 and the conductive member 17 and does not exceed the melting point of the protective member 40. The laser irradiation conditions refer to laser output, spot diameter, focal position in the thickness direction of the conductive member 17, moving speed of the laser irradiation device 70, and the like. Moreover, since the protection member 40 and the tab group 15 are in contact with each other at the valleys of the wavy portions 42, the contact area is small. Therefore, even if a welding process is performed, the protection member 40 is not welded to the tab group 15. After the welding process, a removing process for removing the protective member 40 is performed. Thereby, the lid terminal assembly W is completed. The removed protective member 40 is used in a welding process when another secondary battery 10 is manufactured after the adhering spatter S or the like is removed.

  In the attaching step, the insulating cover 50 is attached to the lid terminal assembly W from the other end side in the stacking direction toward the one end side. The case side insulating portion 51 of the insulating cover 50 covers the tip end portion of the tab group 15 from the other end side in the stacking direction. The lid-side insulating portion 52 is disposed between the inner surface 14a of the lid 14 and the electrode joint portion 17a of the positive and negative electrode conductive members 17. The tab side insulating portion 53a of the negative electrode side insulating portion 53 is disposed between the negative electrode tab group 15 and the tab side end surface 12a of the electrode assembly 12, and the terminal side insulating portion 53b is a terminal joint of the negative electrode conductive member 17. It arrange | positions between the part 17b and the tab side end surface 12a of the electrode assembly 12. FIG. The tab-side insulating portion 54 a of the positive-side insulating portion 54 is disposed between the positive-electrode tab group 15 and the tab-side end surface 12 a of the electrode assembly 12, and the terminal-side insulating portion 54 b is connected to the terminal of the positive-electrode conductive member 17. It arrange | positions between the part 17b and the tab side end surface 12a of the electrode assembly 12. FIG.

  In the housing step, the lid terminal assembly W to which the insulating cover 50 is attached is housed in the case 11. When the electrode assembly 12 and the insulating cover 50 are accommodated in the case main body 13, the case-side insulating portion 51 of the insulating cover 50 is positioned between the tip end portion of the tab group 15 and the inner surface of the case main body 13. And the case main body 13 and the lid | cover 14 are joined by welding, and the secondary battery 10 is completed.

The operation and effect of this embodiment will be described.
(1) In the welding process, the protection member 40 having a plurality of holes 41 is used. Thereby, the laser irradiated from the laser irradiation device 70 passes through the hole 41 and reaches the tab group 15. Since the tab group 15 starts to melt from the portion exposed from the hole 41 of the protection member 40, the welded portion 45 can be formed without melting the protection member 40. Therefore, the time required for the welding process can be shortened as compared with the case where a protective member without holes is used.

  Further, when welding is performed without using the protection member 40, conventionally, laser irradiation is performed while pressing a portion outside the portion of the tab group 15 where the welded portion 45 is formed with a jig or the like. At this time, in the tab group 15, the portion pressed by the jig is preferably in the vicinity of the portion irradiated with the laser. However, since the welded portion 45 is formed in a planar shape, the portion pressed by the jig may be brought closer to the portion irradiated with the laser depending on factors such as interference between the jig and the laser irradiation device. There may not be. In this case, it has been difficult to press the tab group so that the lifting of the tab is restricted over the entire portion where the weld is formed.

  When the protective member 40 is used, the portion where the hole 41 is not formed is adjacent to the hole 41, so that the entire portion where the hole 41 is not formed is near the portion irradiated with the laser in the tab group 15. Can be pressed. Therefore, by using the protection member 40, the tab 26 can be prevented from being lifted over the entire portion of the tab group 15 where the welded portion 45 is formed. As a result, poor welding between the tabs 26 can be suppressed. Further, since it is not necessary to melt a portion of the protective member 40 where the hole 41 is not formed, the protective member 40 is made thick in order to give the protective member 40 sufficient strength to press the tab group 15. it can. Therefore, the tab group 15 can be sufficiently pressed toward the conductive member 17 by the protective member 40. As a result, poor welding between the tab group 15 and the conductive member 17 can be suppressed.

  (2) The protection member 40 has a three-dimensional structure. The rigidity of the protection member 40 with respect to the stacking direction of the tabs 26 is such that the plate material after being processed to have a three-dimensional structure is used as compared to the case where the protection member 40 is a plate material before being processed to have a three-dimensional structure. The case where it is set as the protection member 40 is higher. Therefore, deformation of the protection member 40 when the protection member 40 is pressed toward the tab group 15 can be suppressed.

  (3) The laser irradiation device 70 irradiates a continuous wave laser while moving in the longitudinal direction of the protection member 40 so as to straddle the plurality of holes 41 of the protection member 40. For this reason, in the tab group 15, as in the case of pulse welding, portions that are irradiated with laser and portions that are not irradiated appear alternately. Therefore, an operation corresponding to adjustment of the cycle (frequency) of the pulse current and the base current in pulse welding can be performed only by changing the arrangement of the holes 41 of the protection member 40. In particular, when welding is performed at a high speed in order to shorten the time required for the welding process, it is necessary to increase the moving speed of the laser irradiation device 70 and shorten the cycle of the pulse current and the base current. However, if it is attempted to shorten the cycle of the pulse current and the base current, it becomes difficult for the laser irradiation apparatus to follow the cycle in pulse welding. On the other hand, in the present embodiment, the period of the pulse current and the base current can be shortened only by shortening the interval between the holes 41 of the protection member 40 in the moving direction of the laser irradiation device 70.

  (4) The tab group 15 and the conductive member 17 are welded by keyhole welding. In keyhole welding, the laser repeats multiple reflections in the keyhole H, so that the energy of the laser is efficiently absorbed by the tab group 15 and the conductive member 17. Therefore, compared with heat conduction type welding, the energy of the laser necessary for ensuring the penetration depth of the welded portion 45 can be reduced. As a result, it is possible to suppress the fusing of the tab 26 located on one end side in the stacking direction among the plurality of tabs 26 constituting the tab group 15.

  (5) If spatter S generated in the welding process scatters and adheres to the electrode assembly 12 or the like, the spatter S becomes a foreign matter in the secondary battery 10, which is not preferable. On the other hand, in this embodiment, the protective member 40 is disposed above the welded portion 45. For this reason, scattering of the sputter | spatter S can be suppressed because a part of generated sputter | spatter S adheres to the protection member 40. FIG. As a result, the generation of foreign matter in the secondary battery 10 can be suppressed.

  (6) In the welding process, the metal vapor tends to be ejected from the surface of the tab group 15. On the other hand, in this embodiment, since the protection member 40 is arrange | positioned above the welding part 45, the ejection of a metal vapor is controlled by the protection member 40. FIG. The molten metal is further expanded toward the conductive member 17 by the amount of metal vapor whose ejection is restricted. For this reason, the penetration depth of the welding part 45 can be made deeper. Therefore, it is possible to reduce the laser energy necessary to ensure the penetration depth of the weld 45. As a result, it is possible to suppress the fusing of the tab 26 located on one end side in the stacking direction among the plurality of tabs 26 constituting the tab group 15.

(7) The manufacturing method of the secondary battery 10 includes a removal step of removing the protective member 40 after the welding step. For this reason, the protection member 40 can be used repeatedly.
(8) The protection member 40 is an expanded metal manufactured by extending a metal plate having a plurality of slits. For this reason, for example, the cost of the protection member 40 can be reduced compared with the case where the wave-like plate-shaped member in which the several through-hole was formed is used as a protection member. Moreover, since the peaks and valleys of the expanded metal are inclined with respect to the laser irradiation direction, the laser light is reflected by the protective member 40 and the laser light is suppressed from being absorbed by the protective member 40. Therefore, the protection member 40 is not easily melted, and the protection member 40 can be used repeatedly.

This embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
In the positive electrode 21, the positive electrode active material layer 25 may exist on one side of the positive electrode metal foil 24. Similarly, in the negative electrode 22, the negative electrode active material layer 28 may exist on one side of the negative electrode metal foil 27.

  The terminal structure 16 may not have a structure including all the lead terminals 31, the terminal joining members 32, the external connection terminals 33, and the conductive members 17. In the terminal structure 16, for example, the lead terminal 31, the terminal joining member 32, and the external connection terminal 33 may be changed to rod-like terminals that penetrate the lid 14. One end of the terminal is joined to the conductive member 17, and the other end of the terminal protrudes outside the case 11. In this case, an insulating ring member is disposed between the outer peripheral surface of the terminal and the inner peripheral surface of the through hole of the lid 14 to insulate the terminal and the lid 14. When the rod-shaped terminal has a sufficient cross-sectional area, the conductive member 17 may be omitted and the tab group 15 may be directly welded to the end face of the terminal.

(Circle) you may change the material of the protection member 40 suitably. For example, the material of the protective member 40 disposed on the positive electrode tab group 15 may be nickel (melting point: about 1455 degrees) or invariant steel (melting point: about 1426 degrees). Since nickel hardens significantly with the expanding process, the deformation of the protective member 40 when the protective member 40 is pressed toward the tab group 15 can be suppressed. The invariant steel is an Fe—Ni alloy having a predetermined composition ratio (see Japanese Patent Laid-Open Nos. 59-173241 and 2010-260072), and has a linear expansion coefficient of 1 × 10 ⁻⁶ / ° C. Since it is small, expansion of the protection member 40 during laser welding can be suppressed. Therefore, the protection member 40 can be accurately positioned with respect to the tab group 15.

○ The protection member 40 may not have a three-dimensional structure. That is, a flat plate that has not been processed to have a three-dimensional structure may be used as the protection member 40.
The protective member 40 having a three-dimensional structure is not necessarily an expanded metal. The protective member 40 having a three-dimensional structure may be, for example, a wavy plate-like member having a plurality of through holes penetrating in the stacking direction of the tabs 26, or a plate-like member obtained by pressing a planar net-like member into irregularities. Good.

  (Circle) you may change the aperture ratio of the protection member 40 suitably. The higher the opening ratio of the protection member 40, the larger the range in which the weld 45 is formed. On the other hand, the lower the aperture ratio of the protective member 40, the more the spatter S can be scattered.

  As shown in FIG. 6, the welded portion 45 may be formed by welding the tab group 15, the conductive member 17, and the protective member 40. In this case, in the welding process, the protective member 40 is welded to the tab group 15 and the conductive member 17 and the removal process is omitted. Further, when the insulating cover 50 is attached to the lid terminal assembly W in the attaching step, the tab side insulating portions 53 a and 54 a are inserted between the protection member 40 and the tab side end surface 12 a of the electrode assembly 12. At this time, the tab-side insulating portions 53a and 54a may come into contact with the protective member 40. However, since the protective member 40 is elastically deformed in the stacking direction of the tabs 26, attachment of the insulating cover 50 is not hindered.

The position where the pressing device presses the protection member 40 is not limited to the end of the protection member 40, and may be changed as appropriate as long as the laser is not irradiated.
The laser irradiation device 70 does not have to reciprocate in the short direction of the protection member 40 as long as it moves across the plurality of holes 41 of the protection member 40. In this case, the welded portion 45 is formed in a line shape.

  The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. In short, any ion may be used as long as ions move between the active material for the positive electrode and the active material for the negative electrode and charge is transferred.

  The power storage device can also be applied to power storage devices other than secondary batteries, such as capacitors.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery as power storage device, 12 ... Electrode assembly, 12a ... Tab side end surface, 15 ... Tab group, 16 ... Terminal structure, 17 ... Conductive member, 21 ... Positive electrode as electrode, 22 ... As electrode Negative electrode, 26 ... tab, 31 ... lead terminal, 40 ... protective member, 41 ... hole, 45 ... welded part, 53a, 54a ... tab side insulating part as insulating member, 70 ... laser irradiation device.

Claims (5)

An electrode assembly having a tab group in which a plurality of electrodes are stacked and a tab protruding from one edge of the electrode is stacked;
A terminal structure for connecting the electrode assembly and an external device;
A welded portion laser-welded in a state where the tab group and the terminal structure are overlapped;
A method of manufacturing a power storage device comprising:
When the direction in which the tabs constituting the tab group are stacked is a tab stacking direction, a protective member having a plurality of holes penetrating in the tab stacking direction is used.
An arrangement step of arranging the tab group between the terminal structure and the protective member;
A welding step of forming the welded portion while pressing the protective member toward the tab group;
Including
In the welding process, the laser irradiation device irradiates the laser from the protection member side toward the tab group and moves the laser irradiation device so as to straddle the plurality of holes. Production method. The terminal structure includes a plate-like conductive member on which the welded portion is formed, and a lead terminal connected to the conductive member and connecting the inside and outside of the power storage device,
The method for manufacturing a power storage device according to claim 1, wherein the protective member has a three-dimensional structure.   The manufacturing method of the electrical storage apparatus of Claim 1 or Claim 2 including the removal process which removes the said protection member after the said welding process. In the welding step, the protective member is welded together with the tab group and the terminal structure,
An attachment step of inserting an insulating member between the protective member welded to the tab group and a tab side end surface of the electrode assembly having the tab group;
3. The method for manufacturing a power storage device according to claim 2, wherein, in the attaching step, when the insulating member comes into contact with the protective member, the protective member elastically deforms in a stacking direction of the tabs. The manufacturing method of the electrical storage apparatus as described in any one of Claims 1-4 in which an expanded metal is used for the said protection member.